This project is directed at delineating the cellular and molecular mechanisms of the immunopathogenesis of human immunodeficiency virus (HIV) infection. We have continued to delineate the inductive and suppressive effects of immunoregulatory cytokines on HIV expression. Extending our previous observations on the effects of tumor necrosis factor-alpha (TNF-alpha), interleukin-6, transforming growth factor-beta and granulocyte macrophage-colony stimulating factor, we have further demonstrated a synergistic induction of NF-kappaB dependent HIV transcription in chronically infected Ul promonocytic cells with interferon-alpha (IFN-gamma) and TNF-alpha in association with terminal cell differentiation. IFN-gamma appeared to block HIV induction in Ul cells stimulated with PMA, when in reality it actually redirected virion production from the plasma cell membrane into the intracytoplasmic vacuoles creating an intracellular reservoir of HIV. We demonstrated that SP-1 promoter regions are essential for high constitutive expression of HIV while NF-kappaB binding activity may rescue transcription for SP-1 mutants if cells are treated with TNF-alpha. Site directed mutagenesis of the NF-kappaB p50 protein has delineated regions that are necessary for protein binding and dimerization. A platelet activating factor antagonist (RP55778) was shown to block HIV expression in Ul cells stimulated with PMA or multiple cytokines. We demonstrated that lymphoid organs are the major reservoirs for HIV-infected cells and the predominant anatomic sites for virus replication in that substantial virus replication occurs in the lymph nodes even early in the course of infection when HIV replication is low to absent in peripheral blood during clinical latency. HIV-mediated syncytia formation was shown to be dependent on the LFA-1/ICAMS 1,2,3 pathway of cell to cell adhesion. We demonstrated that distinct sets of V-beta families are perturbed in circulating T cells in HIV infected individuals. Human keratinocytes produce TNF-alpha in response to UV-B irradiation which is capable of inducing HIV expression in chronically HIV infected cells. we have shown that although CD34 + progenitor cells in bone marrow can be infected in vivo and in vitro with HIV the bone marrow does not appear to be a major reservoir for the virus.